Trauma - circulation

Shock

• Abnormality of circulatory system that results in inadequate organ perfusion and tissue oxygenation
• Early identification is crucial
  • Classify it as haemorrhagic or non-haemorrhagic shock (cardiogenic, cardiac tamponade, tension PTX, neurogenic, septic). Be aware that they probably ALL improve transiently with some IVF
• Then initiate treatment based on probable cause
  • Haemorrhage is most common cause in trauma

Types of shock seen in trauma (see separate topic 'Shock' for pathophysiology)

• Haemorrhagic shock
• Cardiogenic
  • Aetiology - blunt cardiac injury, tamponade, air embolus, MI
  • Suspect when mechanism of injury to thorax involves rapid deceleration
  • Put continuous ECG monitoring on thoracic trauma patients
  • Tamponade - Beck's triad - muffled heart sounds, distended neck veins, hypotension (also tachycardia and minimal response to IVF)
    • Need to think about PTX if these signs are present too
• Tension PTX
  • Shift of mediastinum to opposite side (AWAY)
  • Impaired venous return and fall in cardiac output
  • Acute respiratory distress, subcutaneous emphysema, absent unilateral breath sounds, hyperresonance to percussion, tracheal shift
  • Needle decompression followed by chest tube
• Tamponade
• Neurogenic shock
  • Isolated intracranial injuries do not cause shock
  • Hypotension without tachycardia or cutaneous vasoconstriction. No narrowed pulse pressure.
  • Look for thoracic/lower cervical trauma
  • Won't respond to IVF
• Spinal shock

Goals of treatment: to control haemorrhage and restore adequate circulating volume

Primary and secondary survey should pick it up

• Assume any patient who is cool to the touch and tachycardic to be in shock
• VBG - look at base deficit and lactate levels rather than Hb or haematocrit
• Evaluate pulse pressure rather than SBP in early shock

Management:

• Class I: monitor
• Class II: Crystalloid
• Class III: Probably blood
• Class IV: blood +/- MTP
• A/B: Provide supplementary oxygen
• C:
  • Control bleeding ("Just Do It")
    • Permissive hypotension can be considered while getting control of lacerating/penetrating trauma bleeds, but not blunt
    • Direct pressure
    • Splinting
    • Tourniquet
    • Angiography
    • REBOA
    • Resuscitative thoracotomy
    • Damage control surgery
  • Obtain adequate IV access
    • Rate of flow is proportional to the fourth power of the radius of the canula and inversely related to its length ("Poiseuille's Law")
    • Give 1L stat in adults or 20mL/kg in paeds (if they weight < 40kg)
  • Assess perfusion
• D
  • LOC gives useful information for level of haemorrhage
• E: Do the above then complete examination, but avoid hypothermia
  • Consider gastric decompression (avoid gastric dilation)
  • Consider IDC

Define patient as 'rapid responder', 'transient responder', or 'non-responder'

• Transient or non responders need blood! And operative/angiographic haemostasis. Maybe MTP.

Haemostatic resuscitation

• Resuscitate
  • Aggressively control haemorrhage
  • Permissive hypotension - aim SBP 90mmHg
  • Fluids
    • Limit crystalloids - increases risk of ARDS and compartment syndrome
    • Dilutes coagulation factors
    • Increases blood loss
    • Worsens hyperchloraemic acidosis
    • Worsens inflammation
    • May lead to ileus
  • Blood products - target Hb 70-99
  • Tranexamic acid
  • Ensure normothermia
• Monitor for improvement
  • Urine output: 0.5mL/kg/hr in adults, 1ml/kg/hr in paeds, 2ml/kg/hr in <1yo
  • CNS function
  • Skin colour
  • BP and pulse pressure
    • Don't equate an improved BP with resolution of shock - may not reflect a change to cardiac output
  • VBG - respiratory alkalosis in early haemorrhagic shock from tachypnoea. If severe metabolic acidosis develops, you're in trouble.
  • Watch closely for 'lethal triad'
    • Hypothermia
    • Acidosis
    • Coagulopathy
    • Hypocalcaemia is sometimes added as 'lethal diamond' but this is unnecessary
• Targets:
  • Haemostatic control
  • INR <1.6
  • Fibrinogen >1.5
  • Platelets >50
  • pH >7.20
  • SBP 80-90mmHg
  • Temp >36
• If shock does not respond to fluid:
  • Look for a source of ongoing blood loss (abdo/pelvis, retroperitoneum, thorax, extremities)
  • Consider non-haemorrhagic shock
  • Begin blood and blood component replacement
  • Obtain surgical consultation
  • Consider anticoagulant reversal

Special populations

Elderly

• • Reduced response to catecholamines, more sensitive to small reductions in CO, potential for long-term hypovolaemia
    • = poor tolerance to haemorrhage
  • Reduced cardiac compliance, and can't increase heart rate or contractility when stressed
  • Atherosclerotic vascular occlusive disease makes organs sensitive to slight reductions in blood flow, especially kidneys
  • Medications
  • Reduced pulmonary compliance and weakness of respiratory muscles

Athletes

• • Can compensate better
  • Blood volume up 15-20%
  • Capable of big variations in cardiac output
  • May not manifest usual signs until late

Pregnancy

• • Normal hypervolaemia in pregnancy - blood volume peaks at 34 weeks - 30-50% higher than normal. There is physiological anaemia of pregnancy (normally haematocrit 31-35%). Healthy patients will lose 1.2-1.5L of blood before showing signs of hypovolaemia.
  • WBC higher in pregnancy
  • Levels of serum fibrinogen and other clotting factors mildly elevated, but bleeding and clotting times are unchanged
  • Cardiac output is 30-40% higher normally, but significantly decreased in supine position due to reduced preload from IVC compression
  • Higher baseline HR - 10-15bpm higher
  • Lower baseline BP by 10-15mmHg in second trimester
  • Tidal volume increases and hypocapnia is common - PaCO2 is normally 27-32, and PaCO2 of 35-40mmHg may indicate impending respiratory failure
  • Elevated diaphragm
  • Takes greater blood loss to manifest abnormalities. Can = poor perfusion to fetus
  • Placental vasculature is very sensitive to catecholamine stimulation - reduced fetal oxygenation despite normal maternal vital signs
  • Placental abruption - can occur in the absence of any significant maternal injury
  • Changes to primary survey
    • Manually displace uterus to the left side, or log roll to the left
    • Aim to maintain physiological hypervolaemia of pregnancy with early infusion/transfusion
    • Avoid vasopressors - fetal hypoxia
    • Continuous fetal monitoring after 20 weeks
  • Secondary survey
    • Speculum exam to exclude spontaneous ROM, PV bleeding
    • Fetal assessment - fundal height, contractions/irritability, US/CTG
  • Adjuncts
    • CT has the same indications - CT A/P is about 25mGy, and fetal radiation doses less than 50mGy are not associated with any known fetal anomalies or higher risk for fetal loss. However, exposure to 50mGy ionising radiation increases childhood cancer risk - risk of NOT having cancer goes from 99.8% to 99.5%.
    • All Rh-negative trauma patients should receive Rh immunoglobulin unless the injury is remote from the uterus, within 72 hours

Medications

• • Beta blockers
  • Insulin

Pacemakers/ICDs

• • Unable to respond to blood loss properly
  • Can it be adjusted to increase HR?

MTP: 10 units in first 24 hours, or 4 units in 1 hour

• Balanced pRBCs, plasma and platelets
• See separate topic

Intra-osseous access:

• Identify the puncture site 2cm below the tibial tuberosity, on anteromedial surface
• Attach cannula to drill - usually in the kit, pink is for paediatric, blue for most sites, yellow is longer for humerus or obese patients
  • Medial malleolus where shaft meets ankle
  • Distal femur, anterior, two finger-breadths above wide condyles
  • Humeral head, into greater tuberosity
• Clean skin
• LA?
• Introduce the needle and advance to bone. Fire drill until you feel give and then push into the cavity. Don't advance too far, you'll go into the back wall.
• Attach the needle to a 10mL syringe and should be able to aspirate bone marrow
• Inject saline - if it goes ok, likely correctly located
• Infusion via the catheter  of 2mL 2% lignocaine over two minutes provides good analgaesia